Use Option<[u8; N]> for JoinSplit pubkey and signature in a transaction

zcash_primitives/src/transaction/tests.rs

@@ -156,6 +156,46 @@ fn tx_read_write() {
     assert_eq!(&data[..], &encoded[..]);
 }
 
+#[test]
+fn tx_write_rejects_unexpected_joinsplit_pubkey() {
+    // Succeeds without a JoinSplit pubkey
+    {
+        let tx = TransactionData::new().freeze();
+        let mut encoded = Vec::new();
+        assert!(tx.write(&mut encoded).is_ok());
+    }
+
+    // Fails with an unexpected JoinSplit pubkey
+    {
+        let mut tx = TransactionData::new();
+        tx.joinsplit_pubkey = Some([0; 32]);
+        let tx = tx.freeze();
+
+        let mut encoded = Vec::new();
+        assert!(tx.write(&mut encoded).is_err());
+    }
+}
+
+#[test]
+fn tx_write_rejects_unexpected_joinsplit_sig() {
+    // Succeeds without a JoinSplit signature
+    {
+        let tx = TransactionData::new().freeze();
+        let mut encoded = Vec::new();
+        assert!(tx.write(&mut encoded).is_ok());
+    }
+
+    // Fails with an unexpected JoinSplit signature
+    {
+        let mut tx = TransactionData::new();
+        tx.joinsplit_sig = Some([0; 64]);
+        let tx = tx.freeze();
+
+        let mut encoded = Vec::new();
+        assert!(tx.write(&mut encoded).is_err());
+    }
+}
+
 #[test]
 fn tx_write_rejects_unexpected_binding_sig() {
     // Succeeds without a binding signature